1. IDC HPC USER FORUM Weather & Climate PANEL September 2009 Broomfield, CO Panel questions: 1 response per question Limit length to 1 slide

2. Panel Format Sequence – Alphabetical Few bullet points for each question, each participant can address/supplement it After each panel member has finished it, we move on to the next question Moderators can adjust depending on discussions and time constraints

3. Panel Members Steve Finn & Sharan Kalwani Panel ParticipantAffiliation Jim DoyleDoD HPC Modernization Program Jim HackORNL John MichalakesNCAR Henry TufoUniversity of Colorado

4. Q1. Relative Importance of data/resolution/micro-physics ! Please quantify the relative importance of improvements in observational data, grid resolution, cloud micro-physics for future forecast accuracy ? For prediction 1.Observations and understanding of observations Data assimilation Ensembles 2.Physics Scale appropriate Sensitivities Superparameterizations 3.Resolution Explicitly resolve scales Convergence studies, feed back to prediction

5. Q2. Adaptive Mesh or Embedded Grids: their impact… Please discuss the use of Adaptive Mesh or embedded grids ( urban area, terrain impact on advection..) and how would future increased use of this, impact system requirements such as system interconnects? Nesting Domains interact sequential Scatter-gather 3D fields between domains Spatial refinement In place, adding cells Temporal refinement (future) Adaptivity (future) Coupling Load balancing, bandwidth

6. Q3. Ratio of Date to Compute: Background… What are your Bytes per Flop for future requirements? Assuming the question means “bytes of main memory per sustained flop/s” (D. H. Bailey) Current – lots of headroom ~2000 ops per cell per second ~800 bytes (4 byte floats) per cell = 0.4 bytes per op Future Resolution follows 3/4 rule (2/3 in practice) Adding physics or chemistry should not upset this ratio * This is a relatively *low* ratio compared to some other benchmarks? Geerd Hoffman of DW said 4Bytes/Flop @ the Oct 2007 HPC User Forum in Stuttgart)

7. Q4. Open Source codes in the community… What is the Importance and impact of open source / community code applications such as CCSM, WRF,….? Common modeling tool to foster interaction, outreach, and ultimately advancement of the science Relevant HPC application benchmarks

8. Q5. Data and collaboration, formats, future needs… What is the level of collaboration and standardization of data management, observational & results data bases: such as use of common file formats, web based data, etc. What is needed in the future? Scientific and technical interoperability for multi-model simulation systems Metadata formalisms, conventions, infrastructure: Earth System Curator (www.earthsystemcurator.org) Earth System Grid (www.earthsystemgrid.org)

9. Q6. Ensemble model: your experiences… Has the use of ensemble model had any positive or negative impact in reducing the code scaling requirements? Ensembles have a positive effect on scaling because they are trivially scalable

10. Q7. Obligatory Question: (no pun intended!) Cloud computing: your views (unfiltered)… What is your current / future interest in grid or cloud computing ? Computational grids are not feasible for tightly coupled parallel applications Reproducibility across platforms also an issue Data and observing grids are useful WRF is used in LEAD (portal.leadproject.org)